The prior art shackle lock is generally composed of a body and a shackle of a U-shaped construction. The shackle is engaged at both ends thereof with two insertion holes of the body. Located at one end or the center of the body is a lock core engageable with a key. A shackle lock of a large size is capable of locking two bicycles together or of fastening a bicycle to a tree trunk or a telephone pole. The length of the shackle of such a large shackle lock as described above may be as long as 310 millimeters. It is therefore conceivable that the large shackle lock as such should take up too much of a space in the bicycle rack, and that the shackle and the body can be separated forcibly by means of a jack.